1. Field of the Invention
This invention concerns a metallic powder and a paste made from that powder, and a device for manufacturing that metallic powder.
2. Description of the Prior Art
Powders and pastes obtained through the use of techniques such as the atomization method, the rolling method, the solubility method, and the reduction/mixing method have been known in prior art. However, each of these techniques had advantages and disadvantages: the atomization method gave a bad yield in powder production because the powder thus produced contained a dust-like substance called "fine", while the rolling method or the solubility method could not produce powders with particles of a small enough size and were unsuitable for mass-production, while the reduction/mixing method produced a powder too fine and not suitable as solder. Powder manufacture using a nozzle method had also been previously considered, but because the powder produced had a large particle size, it had not been thought possible to produce the microscopic 20-90 .mu.m size of this invention.
As the density of surface mounting of chips on printed circuit boards has increased, the gaps between the patterns on the printed circuit boards have been reduced. Consequently, the powders or pastes used to surface mount these chips on the printed circuit board must satisfy certain conditions, including but not limited to improvement of flux, such as they must be sufficiently small in size, have good granularity, no fine, and no "dulling" after printing or painting. However, none of the powders or pastes made using former methods were able to satisfy these requirements.